1. Field of the Invention
The present invention relates to an image capture apparatus, an accessory connected to the image capture apparatus, and an image capture system in which the accessory is connected to the image capture apparatus.
2. Description of the Related Art
In general, an image capture apparatus such as a digital camera can connect an accessory such as a flash device. In order to control the connected flash device via an interface used to connect the image capture apparatus and flash device, a communication for transmitting a lighting instruction signal to the flash device can be made. However, when the image capture apparatus is inactive in a power saving mode, data cannot be exchanged between the image capture apparatus and flash device. Hence, in such case, even when the user mounts the flash device on the image capture apparatus and operates operation members on the flash device side, these operation contents are not reflected to the image capture apparatus.
Japanese Patent Laid-Open No. 1-287643 (to be referred to as literature 1 hereinafter) has proposed an arrangement which allows the flash device to activate the image capture apparatus in the power saving mode. According to literature 1, in the flash device, a circuit for transmitting an activation signal in synchronism with activation of the flash device is added to a connection terminal, which receives communication clock pulses from the image capture apparatus. Also, in the image capture apparatus, a circuit for receiving the activation signal from the flash device is added to a connection terminal, which outputs clock pulses to the flash device. That is, according to literature 1, the flash device transmits the activation signal to the image capture apparatus via the clock pulse terminals, and the image capture apparatus which received that signal is activated from an idle state in the power saving mode to a normal active state.
However, with the related art disclosed in literature 1 above, new circuits have to be added to the clock pulse terminals of the image capture apparatus and flash device, thus deteriorating the waveform of communication clocks and disturbing a high communication speed.